In general, when extruding a metal material, for example, a billet of aluminum or an alloy material of the same, by an extrusion press apparatus, the following is performed. An extrusion stem is attached to a front end part of a main ram driven by a hydraulic cylinder. First, in a state with a container pushed against a die, the billet is placed in the container by the extrusion stem etc. Further, a main ram is made to further advance by a drive operation of the hydraulic cylinder. Due to this, the billet is pushed by the extrusion stem. Therefore, a shaped product (extruded material) is extruded from an outlet part of the die.
In the past, when producing a plurality of types of extruded products, the general practice was to finish extruding a single billet inside the container up to its end, exchange the die, then resume extrusion. Further, in the case of a short extruded product, the general practice was to heat a short billet corresponding to the length of the extruded product by a heater and repeatedly alternately exchange the die and perform extrusion. According to PLT 1, the following invention is disclosed. This invention is an extrusion method for an aluminum shape, wherein an aluminum billet is loaded in a container and pressure is applied by a stem to the aluminum billet to extrude it from the die. With this method, when a predetermined length of the aluminum shape is extruded, the container and the stem are made to retract from the die and the aluminum billet is broken between the die and the container. After that, the parts of the aluminum material sticking out from the die and container are cut off by shear knives. Further, the die is exchanged and the billet remaining inside the container is used to resume extrusion.